The classical waste water tank pumping stations employing immersed sewage pumps fixed automatically on a coupling footings immersed in the waste water pumped by them. The pumping station tanks in the developed versions have most commonly beds in a form of cone or sphere, which improves to some extent the hygienic conditions in the pumping stations. Furthermore, they can be equipped with devices controlling the pump performance aiming at elimination of floating rubbish which in turn reduces the water level at the inlet of the immersed pump, and with automatic rinsing valves supporting the pump performance in terms of elimination bed sediments. In such waste water pumping stations the retention share of waste water is contained in the same tank as the immersed pump and the staff has a more direct reach to the waste water upon each entrance to such a tank. This tank is called a wet tank or a wet chamber.
Nevertheless, the conditions of service and operation in such developed pumping stations have not improved noticeably, while their production costs have risen significantly.
Pumping devices placed in dry tanks are more commonly known and used. These include both the waste water pumping devices employing impeller pumps and also air compressors. In comparison to tank pumping stations they provide virtual airtight sealing of the object and its operation can be performed in much cleaner environment In such pumping systems, the retention share of the waste water is contained in a separate retention tank located most frequently on the bed of the dry tank or next to the dry tank, so that the staff does not have the direct contact with the sewage water each time upon entering such a tank. This tank is also called a dry chamber. In case when the dry chamber is located in flooded areas and there is a possibility of its flooding, the hermetic impeller pumps with engine cooled by the passing liquid or immersed impeller pumps adjusted also to dry outdoor operation. Manual pumps or portable immersed pumps are used for the purpose of emptying the waste water overflowed from the retention tank during pump replacement or system inspection.
The main disadvantage of this solution is the difficult operation of tightly packed vertical tanks, pumps and fittings, as well as too deep pump casing in relation to the level of the waste water channel inlet, which significantly rises the costs of production of new waste water pumping devices.
The increasingly higher regulations in terms of environment protection, reliability of pumping systems performance, reduced purchase and maintenance costs influence the attitudes in the branch of water management and waste water disposal towards these problems and thus are a stimulus for the search of new solutions for waste water pumping stations, especially containing solid particles.
Due to this, the expectations of the water management and waste water disposal companies supported by increasingly strict regulations with regard to environment protection in residential areas, human presence near to sewage plants and provision of possibly hygienic conditions for their operation aim towards elimination of unpleasant and dangerous odours, for example by tightening of the sewage systems and their improved performance and reliability.
Therefore, the above factors, among them especially reduction of labour in the waste water environment should be primarily considered with regard to specific solutions of the modern pumping stations.
Thus, it has become necessary to construct such a pumping device which would meet the expectations of the water management and waste water disposal companies, as well as fulfil the strict regulations with regard to environment protection in residential areas and human presence near to waste water treatment facilities and possibly best hygiene for their operation.